Hi all,
First I want to be clear that I really have no clue how to really use any “DAW”, and especially not how to actually use a “plugin”. I feel very accomplished that I can consistently record and export a single track from a single digital microphone in Audacity. I’m trying Ardour since it seems to be well thought of from what I can tell online, and it appears that many users have had success using the “setBfree” virtual instrument, which apparently is a sort that has to be run inside a “DAW”. Also, I seem to have been able to create a new track, which is something.
As far as how I’m running, I’m on Debian 12, and according to “apt install”, ardour is the current version (1:7.3.0+ds0-1). I downloaded setBfree about 40 minutes ago from x42 setBfree - ToneWheel Organ. I think I think I have successfully “installed” setBfree by following the README instructions and coping the b_synth.lv2 into a folder /.lv2 in my home directory, and if I create a new “MIDI track” inside Ardour I can find an option to have it use setBfree. This seems somewhat promising. Unfortunately, after doing the above there is no graphical representation of the instrument, and I don’t know of any way to control it. (I’m testing with no MIDI keyboard attached, in part since with standalone virtual instrument software like Yoshimi, VMPK, and GrandOrgue I’m accustomed to always being to control the instrument with mouse input as well.)
Am I going about this vaguely the right way? Please bear in mind that while I first studied music around 1983, and have used Linux on and off since 2003, I probably lack most knowledge that might be considered common in digital music circles, so it’s quite possible I’ll ask for clarification your 8 year old nephew could provide. 
